Video recording systems are commonly used to monitor places where it may be desirable to monitor security levels. For example, in a security zone, breaches of security may be recorded if video monitors are arranged around the space to be monitored. When an incident occurs, a video record of the related activity is available from the recording system.
During periods when no breaches of security occur, a considerable amount of data is still generated by the video recording system, which has little or no value. Thus, such data can be readily discarded without loss. The act of ‘discarding’ data amounts to merely rewriting new data over old recorded data. Indeed, most video security systems are arranged with a recording medium that is reused continuously.
When a video camera generates an amount of image data sufficient to fully consume the available memory, newly collected data is recorded at the beginning of the memory. Therefore, the act of writing newly acquired data causes old data to be discarded; that is, the old data is lost to the ‘write’ operation of the newly collected data.
In old videotape systems, this is sometimes called a ‘round robin’ arrangement. A memory medium fashioned as a tape in a continuous loop provides data storage for those video security systems. In such systems the tape has no end and no beginning, but instead the tape continuously passes by a recording head where new images are written to the tape and at the same time old images are discarded.
When an incident of interest occurs, the tape may be stopped to prevent loss of data which relates to the relevant incident. The related images may be recovered from the tape and transferred to a permanent medium, while the tape is returned to the video system for further recording. Such re-use of memory is well known in the prior art.
In a round-robin scheme, the data that is overwritten, or discarded, is the data which came into the system earliest, or was ‘first in’ the system. This arrangement is sometimes referred to as “first-in, first overwritten,” which is analogous to the “first-in, first-out” arrangement in electronic buffer systems. In both cases, we will refer to this method as FIFO.
A FIFO base system is generally a very good system for buffer management, because the oldest data in a buffer is typically the least valuable. Therefore, the oldest data, or the least valuable data, may be discarded without regard for its loss. However, in buffer systems the earliest received data, or the ‘first-in’ data, may not always be the least valuable data. In some instances it may be advisable not to overwrite the oldest data, but rather to provide an overwrite scheme which preserves certain portions of interest of the oldest data.
With specific reference to the monitoring of vehicle activities, vehicle event recorders are video recorder systems mounted within the vehicle to provide a video record related to the environment surrounding a vehicle during its operation. These systems are known in the art and are employed, for example, in conjunction with police activity. Many police departments in the United States are equipped with vehicle event recorders, which capture activity, sometimes criminal, occurring in the proximity of a police vehicle.
The application of vehicle event recorders is not limited to police vehicles. More and more commercial vehicles are now equipped with systems that record activity associated with the use of the vehicle and within the environments in which the vehicle is used. These systems are particularly advantageous with fleet vehicles that are subject to heavy professional use and frequent incidents, including traffic accidents, theft, and vandalism, among others. With a video record, vehicle fleet managers are better equipped to manage and control costs associated with operations of large vehicle fleets. Safety is improved, driver performance is improved, a better understanding of accidents is achieved, and other benefits are derived from the use of vehicle recorder systems.
Vehicle recorder systems are described, for example, in U.S. Pat. Nos. 6,389,340, 6,405,112, 6,449,540, and 6,718,239, all to Rayner. In general, these inventions relate to a small device mounted on the vehicle rearview mirror to capture video images of traffic incidents ahead of the vehicle.
In particular, the '112 patent discloses a system that includes a vehicle operator performance monitor, which records a video of the vehicle operator, and which may be used to determine how the operator's actions affect use of the vehicle.
The '540 patent instead is an event recorder mounted in a vehicle, which includes one or more wave pattern detectors for detection and recognition of a predetermined wave produced outside the vehicle, and for producing a trigger signal denoting the presence of the predetermined wave. In particular, a detective wave is a wave of the type produced by a police or fire department emergency vehicle. Detection of this wave triggers a capture function which stores video images a long-term storage memory.
The '329 patent includes a video recorder system having a one-way hash function to perform a validation function. This way, the integrity of the recorded video data can be protected.
Finally, the '340 patent teaches a recording system having a certain relationship between two different types of memory. A first memory is arranged to store video for the short-term and to transfer some of that stored video in response to a trigger event. Data from this short term memory is transferred to a more durable and long-term memory, and the short term memory is continuously overwritten in a scheme described by Rayner as “first-in, first-overwritten”. This way, Rayner teaches the coupling of a high-speed, high-performance volatile semiconductor memory with a flashlight memory good for long-term storage of large amounts of data even when power is removed. As will be described in detail later, Rayner's first in first overwritten scheme necessarily creates a loss of important and valuable data.
While systems and inventions in the prior art are designed to achieve particular goals and objectives, these inventions also include limitations which prevent their use in more extended applications, and cannot be used to realize the advantages and objectives of the inventions taught hereinafter.